During the microbiological preparation of vitamin B.sub.12 and other corrinoids, vitamin B.sub.12 produced by microorganisms is accumulated substantially intracellularly, and therefore is generally isolated from the fermentation broth by isolating the cell mass, e.g. by filtration, sedimentation and/or centrifugation, and disrupting the cells in the so called cell-cream (bio-mass) obtained (which can be utilized, after drying, also directly, as a vitamin B.sub.12 -containing fodder additive). Vitamin B.sub.12 and the accompanying corrinoids are contained in a liquid phase from which they can be isolated by extraction or adsorption methods, after eliminating the cell debris and other solid impurities by filtration and/or centrifugation and optionally further purification or enrichment.
The known processes for the microbiological production of vitamin B.sub.12 and for its isolation from the fermentation broth are for example disclosed in "Vitamin B.sub.12 and verwandte Corrinoide" (R. Ammon: Fermente-Hormone-Vitamine, III/2, G. Thieme Verlag, Stuttgart, 1975, 10-13).
According to the known processes the separation of the microorganisms containing the corrinoids from the fermentation broth has technical difficulties and often cannot be carried out with a satisfactory yield. A further problem is that the fermentation broth contains vitamin B.sub.12 in a relatively low concentration, accompanied with a large amount of partly suspended, partly dissolved impurities; hence it is very difficult to find a technically suitable and economic method for the isolation of the active ingredient from its low level solution obtained after the disruption of the cells. These difficulties are particularly serious when the fermentation medium is inoculated with sludge (e.g. methane-forming septic fermentations), since in these cases the corrinoids produced must be separated from considerably more accompanying impurities, which are more difficult to eliminate than in case of sterile fermentation, for example with Propionibacteria.
There have been numerous attempts to eliminate the above difficulties, using various additional purification or enrichment steps to facilitate the isolation of vitamin B.sub.12 in high purity.
According to the Hungarian Patent Specification No. 158,809 the cells are separated from the fermentation broth of Propionibacterium shermanii; they are disrupted and the pH of the medium is gradually adjusted to 5.5-6.5. Under such conditions a part of the impurities, especially the proteins are bound to the biomass, while vitamin B.sub.12 remains in the solution. The biomass and the accompanying impurities are then separated by centrifugation or sedimentation and vitamin B.sub.12 and other corrinoids are isolated from the purified solution by ion exchange. This process is difficult to carry out on an industrial scale since the separation of the cell debris and the precipitated impurities is cumbersome, and the use of filtration-sedimentation aids may lead to a substantial loss in active ingredient.
According to the Soviet Patent Specification No. 161,709 the complete fermentation broth or the separated biomass is treated by heat in an acidic medium, the solid particles are separated by centrifuging, and the active ingredient is adsorbed from the supernatant by alumina or an ion exchange resin. The micron-size cells and other fine, suspended impurities can, however, not be isolated completely by centrifugation, and in the presence of the residual impurities the effectivity of the adsorption isolation of active ingredient is not satisfactory, and the practical performance of the process is often hindered by serious technical difficulties.
The isolation of certain active ingredients from their fermentation broths containing cells or cell debris and other solid impurities has considerably been facilitated by the application of so called macroreticular adsorption resins. These hard, insoluble, porous, apolar or to a certain degree polar bead polymers having a large specific surface area due to their favorable pore size, grain size and mechanical stability allow even the adsorption of materials dissolved in mixtures containing solid particles, for example by fluidized bed or batchwise operation. Thus the cumbersome filtration or centrifugation of the fermentation broth can be avoided and the whole amount of the fermentation broth can be introduced into the adsorption system. A disadvantage of this method is that in addition to the active ingredient a considerable amount of impurities is adsorbed on the resin. Processes based on the principle described above can be employed also when the corrinoids are the active ingredients in the fermentation medium, since it is known (U.S. Pat. No. 3,531,463) that some macroreticular adsorption resins adsorb corrinoids from their aqueous solutions, and the corrinoids can be eluted from these resins with suitable solvents. However, until now there has been no process known in the art for the adsorption of corrinoids from fermentation broths, which, in addition to the elimination of the disadvantages of other known processes, could have been carried out easily and could have provided the active ingredient in satisfactory purity and with a good yield.